Hi... My Father, Aged 77 Years Is A Patient Of

Hi... My father, aged 77 years is a patient of Alzheimer starting stage. He is on Aricep-5 morning and Aricep-5 late evening alongwith Serta per day. He is experiencing unusual tiredness and weakness. This feeling increased and added drowsiness too when his late evening Aricep power was increased to 10mg couple of days back. Now 15mg Aricep per day. Kindly advise how to mitigate this tiredness and drowsiness.